<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            font-size: 30px;
        }
        .txt1{
            /* 大写字母转小写 */
            text-transform: lowercase;
        }
        .txt2{
            /* 小写字母转大写 */
            text-transform: uppercase;
        }
        .txt3{
            /* 首字母大写 */
            text-transform: capitalize;
        }
        .txt4{
            /* 不转化 */
            text-transform: none;
        }
    </style>
</head>
<body>
    <div class="txt1">ABCDEFGHJSL</div>
    <div class="txt2">dfajhwnjmad</div>
    <div class="txt3">ajuhahncuar</div>
    <div class="txt4">ajuhahncuar</div>
</body>
</html>